Today, carbon dioxide (CO2) is a hot topic. Scientists around the globe are searching for ways to store, dispose of, or prevent the formation of the greenhouse gas, which is a major driver of global climate change. Liquid Light hopes to take this concept one step further and harness waste CO2 as a source of carbon to make industrial chemicals and fuels.

Take CO2 and mix it in a water-filled chamber with an electrode and a catalyst. The ensuing chemical reaction converts CO2 into a new molecule, methanol, which can be used as a fuel, an industrial solvent or a starting material for the manufacture of other chemicals.

Cole set up a flask containing a solution of CO2 and a pyridinium catalyst dissolved in water. In place of sunlight, which emits a broad spectrum of wavelengths of light, she shined on the flask a blue light-emitting diode (LED) because it gives off certain wavelengths that are highly efficient at driving the reaction. In the flask she placed an electrode that is activated by particles of light, or photons. "We used a semiconductor electrode that would allow us to substitute light for electricity," said Cole.

Bocarsly likes to call the process "reverse combustion" because it is like running a burning reaction backwards. Instead of burning fuel and oxygen to produce CO2, the CO2 converts back into fuel and oxygen.

The Princeton scientists did some additional studies, and made a surprising discovery: They could turn CO2, which contains only one carbon, into a compound with a carbon-carbon bond, which vastly increases the possibilities for creating commercial applications.